Both 32-bit and 64-bit versions of Firefox can be installed on 64-bit Windows and Linux operating systems. See this blog post to learn more.
Not sure whether you're running 32-bit or 64-bit Firefox? This article explains how to find out.
"About Mozilla Firefox" window
You can find what version of Firefox you are using in the "About Mozilla Firefox" window. Click the menu button 
, click and select .Click the menu button , click Help and select . The "About Mozilla Firefox" window will open. (32-bit) or (64-bit) will be shown below the Firefox name, next to the version number.
Here is an example of what the "About Mozilla Firefox" window will look like:
Windows program listing
You can also check the installed version of Firefox from the Windows list of installed programs. Open the Windows Control Panel, click on , then .Open Windows Settings, click on , then . This will show you a list of software that is currently installed on your computer.
To see if the 32-bit or 64-bit version of Firefox is installed, locate Mozilla Firefox in the list of programs. The program name will be followed by the the bit version and language, in parentheses. If the program name contains x86, the 32-bit version of Firefox is installed. If the program name contains x64, the 64-bit version of Firefox is installed.
